Tachypnoea refers to an increased respiratory
rate whereas the term dyspnoea, in veterinary medicine at least, is usually used
to describe laboured or difficult breathing.
Tachypnoea should not be confused with
panting which is a normal thermoregulatory mechanism in the dog. Whereas dogs
are neither nasal nor oral obligate breathers, cats under normal circumstances
are nasal breathers and oral breathing only occurs in disease situations.
Dyspnoea is a slow and purposeful form
of respiratory distress and can be difficult to identify accurately in tachypnoeic
individuals. Dyspnoea is best appreciated on close observation and auscultation,
and can be either inspiratory or expiratory.
If the inspiratory difficulty is associated
with the large upper airways it is called stridor. If airflow is very turbulent,
particularly in association with the nasal passages and pharynx, a snoring noise
occurs which is called stertor.
Expiratory dyspnoea is heard as a reasonably
discrete end-expiratory effort or grunt, and might only be heard on auscultation.
The movement of the abdominal wall during rapid breathing should not be confused
with expiratory dyspnoea, unless the abdominal wall movement is associated with
audible expiratory dyspnoea.
If tachypnoea and dyspnoea occur together,
the term hyperpnoea is used.
Orthopnoea is dyspnoea where the individual
adopts an unusual position, such as sternal recumbency, with the elbows abducted,
the neck extended and mouth breathing. This indicates severe respiratory impairment.